LAUSR

Background Evidence regarding whether prenatal exposure to air pollution increases the risk of hypospadias is limited. Objectives The aim of the study is to evaluate the association between exposure to ambient air pollution during early pregnancy and occurrence of hypospadias. Methods We conducted a 1:10 case-control study using the Taiwanese Birth Registry database. Those male births reported to have hypospadias were defined as cases; while controls were randomly, matched by birth year, selected from those male births without any congenital anomaly. Monthly average of ambient air pollutants, including PM10, PM2.5, NO2, NOx, and O3, from three months pre- to six months post-conception were retrieved from the 76 air quality monitoring stations and interpolated to the level of township using empirical bayesian kriging. Potential covariates to be adjusted included gestational age, birth weight, birth season, maternal age, maternal diabetes and hypertension, maternal smoking, annual household income and population density of the residential township. Results During 2007–2014, a total of 265 hypospadias was reported, and 230 (87%) of them were full-term births. Results of multivariate logistic regression models revealed that for per IQR increase of O3 (8.0 p.p.b) exposure during the first months after conception increased the risk of hypospadias (aOR=1.38, 95% CI=1.07–1.78). In subgroup analysis of full-term births, we further found that PM2.5 exposure during the first three months post-conception significantly increased the risk of developing hypospadias (aOR=1.29, 95% CI=1.01–1.65, per IQR=15.4 ug/m3). Conclusions The results of the study suggested that early gestational exposure to ambient air pollution increased the risk of hypospadias occurrence.